Tetrahymena pyriformis will be incubated with C14-labeled substrates -glucose, fructose, ribose, and glycerol - with all substrates present but only one substrate labeled in any given flask. Measurements will be made of label incorporation into glycogen, CO2, and the fatty acyl and glycerol moieties of the lipids. A model of carbon flow (on an atom by atom basis) along the glycolytic and pentose phosphate shunt pathways will be drawn, solved algebraically and equations will be obtained predicting the steady-state flux of label into each of the products measured for any given set of flux parameters of the metabolic pathways. An attempt will be made to fit the experimental data to the model by using a computer to find a consistent set of flux parameters that will reproduce the experimental data. Since preliminary data indicate that this portion of intermediary metabolism does not proceed under steady state conditions for several hours after the initial addition of glucose and fructose, data will be obtained at various times after addition of the labeled substrates and will be analyzed by a quasi-steady state approximation for various sub-intervals of the total duration of the experiment. BIBLIOGRAPHIC REFERENCES: Eldan, M. and Blum, J.J. 1975. Presence of Nonoxidative Enzymes of the Pentose Phosphate Shunt in Tetrahymena. J. Protozool. 22, 145-149. Raugi, G.J., Liang, T. and Blum, J.J. 1975. Effect of Oxygen on the Regulation of Intermediate Metabolism in Tetrahymena. J. Biol. Chem. 250, 445-460.